1. Field of the Invention
The invention refers to a plunger or mold form for supporting a preformed wall against deformation from expanding and hardening foamed plastic on the other side of the wall. The invention furthermore refers to a method for making such a plunger.
2. Description of the Related Art
In making a common type of refrigerator door having an outer wall of sheet metal and an inner wall of plastic, the walls are placed in a fixture, the space between the walls thereafter being filled with expanding and hardening plastic foam. The purpose of the fixture is to support the walls against the overpressure exerted by the foam before it has hardened and thereby prevent the walls from changing form. It is particularly important that the fixture supports all parts of the inner wall which are relatively weak and often have a very irregular form. For this purpose, this part of the fixture is constituted by a detachable plunger which accurately conforms to the inner wall, so that is shows a substantially complete impression of the inner wall, the plunger supporting the wall by said impression.
It can take 8 minutes for the foam to harden in the space between the walls. On multiple production of one refrigerator per minute, 8 fixtures with 8 identical plungers therefore might be needed. A manufacturer of refrigerator doors can make door types showing inner walls of e.g. 60 different forms. This requires 8.times.60=480 plungers. It is known to make such plungers of wood or metal having the drawback of being very expensive. Another drawback with the large number of plungers is that they take valuable space in the factory.